Color photographic elements typically contain several records each with silver halide sensitized to a different region of the visible light spectrum. Generally, one record is sensitized to red light, another green light and another, blue light. Each of the foregoing records also contains a color coupler which reacts with oxidized developer during processing of the element, to produce a dye in a pattern corresponding to the image to which the element was exposed. In a typical element the red, green and blue sensitive records respectively contain a cyan dye forming coupler, a magenta dye forming coupler and a yellow dye forming coupler.
As to the colour couplers, these are known to belong to a number of classes, for example magenta dye-forming couplers can be pyrazolones, pyrazolotriazoles and pyrazolobenzimidazoles while yellow dye-forming couplers can be acetanilides. European Patent Specification 0 431 374 A describes .beta.,.gamma.-unsaturated nitriles as cyan colour couplers of the general formula: EQU R.sub.2 --V.dbd.C(R.sub.1)--CH(W)--CN
wherein W is hydrogen or an atom or group capable of being released when the compound is subjected to a coupling reaction with oxidised product of an aromatic primary amine derivative and is attached to a carbon atom having an sp.sup.3 electronic configuration,
R.sub.1 is a substituent,
V is nitrogen or --C(R.sub.3).dbd.,
if V represents nitrogen, R.sub.2 represents a substituent,
if V represents --C(R.sub.3).dbd., R.sub.2 and R.sub.3 each represent a substituent, provided that at least one of R.sub.2 and R.sub.3 represent an electron attractive substituent, and provided that if R.sub.2 or R.sub.3 represents an aliphatic group or an aromatic group, the other does not represent an acyl group, and
R.sub.1 and R.sub.2 may bond together to form a ring.
The couplers of the above general formula are said to have less subsidiary absorption in the blue region of the spectrum. In support of this contention one drawing (FIG. 1) and a table of data are provided wherein the dye formed from Coupler 53 is compared to that from Comparative Compound (1)--a phenolic coupler.
The color couplers used in the photographic elements of the present invention, as described below, are distinct from those of European Specification 0 431 374A because, inter alia, the coupling position is a carbon atom having an sp.sup.2 electronic configuration and the compounds are .alpha.,.beta.-unsaturated. No examples of them appear in EP 0 431 374A, nor is any method of making them disclosed.
"Preparation and Reactions of 1,2-dicyano-1,2-disulfonylethylenes" by E L Martin, Journal of the American Chemical Society, Aug. 20, 1963 at page 2449, describes compounds of the formula: EQU RNH--C(CN).dbd.C(CN)--SO.sub.2 R.
The method of preparation means that only compounds having the --SO.sub.2 R can be prepared. In addition there is no disclosure of ballasted compounds.
The dyes that are formed by any color coupler during processing have a tendency to fade over time particularly as a result of exposure to light. As all three image dyes of a typical color element fade, this results in overall fading of the image over time. In addition, since the three image dyes may not fade at the same rate, an apparent change in image color also results. Stabilizers are classes of compounds which reduce the foregoing image dye fading problem. Such stabilizers include phenols, bis-phenols, blocked phenols, blocked bis-phenols, metal and other organic complexes and other compounds used in conjunction with many different color couplers. Photographic elements containing the foreogoing color coupler and stabilizer combinations are described, for example, in EP 0 298 321; EP 0 231 832; EP 0 161 577; EP 0 218 266; U.S. Pat. No. 3,043,697; U.S. Pat. No. 3,700,455; Kokai JP 62043-641, JP 01137-258, JP 01144-048; U.S. Pat. No. 4,782,011 and U.S. Pat. No. 4,748,100.
It is desirable then, to provide photographic elements which incorporate a color coupler with advantageous properties, and which elements also incorporate a stabilizer which is effective at stabilizing image dyes formed from such a color coupler.